This invention relates to a large-current fuse having a temperature detection function, in which a temperature detecting fuse for detecting the temperature of a current fuse (main fuse) is provided in the vicinity of a fusible portion of the main fuse. This invention also relates to a method of assembling this fuse.
In a large-current fuse used in a vehicle or the like, its fusible portion is immediately melted when an electric current, larger than 200% of the rated current of the fuse, flows through the fuse. When a current, less than 200% of the rated current of the fuse, flows, the melting time is relatively long since the fuse is designed to withstand a rush current. When not a continuous current but a current as produced at the time of intermittent short-circuiting (rare short-circuiting) flows, the fusible portion of a fuse element repeatedly generates and radiates heat in an element chamber, and the melting time tends to become long. On the other hand, even when an intermittent short-circuiting current flows through a wire constituting a circuit, and the wire does not radiate heat at the time of interruption of the current unlike the fusible portion since the wire is covered with a sheath, and therefore the temperature of the wire continues to rise since the heat is accumulated therein, and in the worst case, there is a possibility that smoke is produced from the wire.
In order to overcome this disadvantage, there has been proposed a large-current fuse having a temperature detection function (hereinafter, a temperature detectable fuse) as shown in. FIG. 5. The temperature detectable fuse 1 comprises a current fuse 3 for being activated by an excessive current, and a temperature detecting fuse 5 for being activated by the ambient temperature, and the two fuses 3 and 5 are mounted in a housing (not shown).
Claws 11, extending from a fuse element 9 of the current fuse 3, are bent or pressed to clamp the temperature detecting fuse 5, thereby holding the temperature detecting fuse 5 on the fuse element 9. Male terminals 13 of the temperature detecting fuse 5 extend outwardly from the housing. The activating temperature of the temperature detecting fuse 5 is set to a value between the maximum temperature, which can develop in a normal condition of use of the current fuse 3, and the activating temperature of the current fuse 3.
In this temperature detectable fuse 1, even at the time of rare short-circuiting when the current fuse 3 is not melted, the temperature detecting fuse 5 is melted to generate a melting signal, so that the circuit can be broken or an alarm can be given to the driver by the signal.
In the above related temperature detectable fuse, however, since the clamping process of the claws can not be carried out so easily, there has been encountered a problem that the productivity is low. And besides, the clamping is conducted after the current fuse and the temperature detecting fuse are inserted into the housing, and therefore the shape of a clamping tool is limited, and the processing has been difficult. If the current fuse and the temperature detecting fuse are beforehand connected together by the clamping, and are mounted in the housing, many terminals must be mounted simultaneously in the housing, which has resulted in a problem that the productivity is low.
In the above related temperature detectable fuse, the temperature detecting fuse is made into a shape of male terminals, and therefore female terminals must be provided in a mating fuse box, which has resulted in a problem that the construction of the fuse box is complicated.